old school post here but still useful for people asking question about 4-2-1 and 4-1 header.

 

eh id say 4 REAL horse.....the power gains are over rated.

 

Isn't it true that it is like a percentage thing so we really don't see that much of an improvement. You go and look at the power gains on a shelby cobra and you see gains of like 30 from a simple CAI. Is this true or just a lie that lets me sleep at night.

 

intake and exhaust have alot to do with percentages... also the 8ish HP gain you see is at the flywheel, so you're looking at about a 3-6 HP gain to pavement. With FI its a different story: the gains will be a little more than double in most cases. A JP performance header for my car shows a 23 HP gain with a supercharger and a 9-10 hp gain with an N/A setup.

 

Can you have headers and a turbo. I was argueing with my friend, I said that the downpipe went there but kinda backed down because I didn't want to fight but I also want to make sure my ish is correct.

 

Yes, you can have both. A turbo is on you intake, the header is on your exhaust.

 

What your friend was probably arguing about is the fact that it's not often referred to as a header... its called a turbo manifold. Its basically the same thing, a standard header for your car wont work with a turbo setup because of the difference in the plumbing... it will need to be custom made or sometimes comes in a kit.

 

in addition to what polo said...a turbo isnt on either the intake or the exhaust. its a whole system to itself. the exhaust drives a turbine then exits. this turbine spins and compresses air (that is taken in the opposite side from the side exhaust gasses leave from) then the air merges with ur incoming air at the throttle body. so its not either

 

close, the air doesnt merge though. the air goes through the turbo and compresses, then goes directly into the TB. and usually when you are talking about a "turbo header" it means a tubular manifold, vs a cast iron log type manifold.